Is there a patch available for CVE-2026-98541?

Yes, a patch is available for CVE-2026-98541. Update the affected software to the latest version immediately.

Linux CVE-2026-98541

EUVD-2026-103586

2026-10-18 Linux

GHSA-rj48-hq74-h6fv

Information Disclosure Linux

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Monitor Track and reassess. Why: No CVSS yet + weak signal (CWE or non-zero EPSS).

Patch available 0.2% exploitation probability (EPSS)

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AnalysisCVE.org

In the Linux kernel, the following vulnerability has been resolved:

fou: reject omitted FOU_ATTR_IPPROTO on FOU_ENCAP_DIRECT

Commit 7a9bc9e3f423 ("fou: Don't allow 0 for FOU_ATTR_IPPROTO.") added NLA_POLICY_MIN(NLA_U8, 1) to fou_nl_policy[FOU_ATTR_IPPROTO], which rejects an explicitly supplied FOU_ATTR_IPPROTO == 0 attribute with -ERANGE.

However, FOU_ATTR_IPPROTO is an optional netlink attribute. When a user sends FOU_CMD_ADD with FOU_ATTR_TYPE set to FOU_ENCAP_DIRECT and omits FOU_ATTR_IPPROTO entirely, nla_policy validation succeeds and parse_nl_config() leaves cfg->protocol as 0 (from memset(cfg, 0, sizeof(*cfg))). fou_create() then creates a FOU_ENCAP_DIRECT socket with fou->protocol == 0.

In fou_udp_recv(), returning -fou->protocol to udp_queue_rcv_one_skb() triggers IP protocol resubmission when fou->protocol > 0, whereas returning 0 tells the UDP tunnel layer that the skb was consumed without freeing it. When fou->protocol == 0, every packet received on the socket returns 0 from fou_udp_recv() and leaks the sk_buff.

Reject FOU_ENCAP_DIRECT when !cfg->protocol in fou_create() so that creating a direct encapsulation port without FOU_ATTR_IPPROTO fails with -EINVAL while leaving FOU_CMD_DEL and FOU_CMD_GET (which share parse_nl_config()) unaffected.

Tested in QEMU against Linux 7.3.0-rc3 by sending a FOU_CMD_ADD Generic Netlink request with FOU_ATTR_PORT = 5555 and FOU_ATTR_TYPE = FOU_ENCAP_DIRECT while omitting FOU_ATTR_IPPROTO. On the unfixed kernel, FOU_CMD_ADD succeeds (err = 0), FOU_CMD_GET reports fou->type = 1 and fou->protocol = 0, and sending 4000 UDP packets to 127.0.0.1:5555 leaks all 4000 sk_buffs (SUnreclaim in /proc/meminfo grows from 41456 kB to 59008 kB, +17552 kB); with this patch applied, FOU_CMD_ADD is rejected with -EINVAL (-22).

Affected VersionsENISA

Linux patch: 6.12.112

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <d22609f3d13fc5baacd92c222731b03c593401db

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <8b43f40798bb2758489fbbcae7e841ad4443c213

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <3bcc1624cc1cdcc05b566475d6e848093ab2a8f6

Linux patch: 5.15.222

Linux patch: 7.3-rc5

Linux patch: 7.2.9

Linux patch: 5.10.271

Linux patch: 6.6.158

Linux patch: 0

Linux patch: 6.18.55

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <520cf06b8ea0ba5bcc1b8b982ef07f02b5e56221

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <b1229b210ef5a39c58be665e6798203751411842

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <fd20220f86947d66d4dba2d76f13a28dbd86ef30

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <46b1ffb7e169c7e401dd890b29e55dbc261f8f01

Linux patch: 6.1.189

Linux 3.18

Linux 23461551c00628c3f3fe9cf837bf53cf8f212b63 <7f4ba56f5d310dd018972916167985010a5d66a1

Affected Packages

euvd linux no fix

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in euvd

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Exploit and PoC references, threat intelligence from 22 sources

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Lifecycle Timeline

Patch available

Oct 18, 2026 - 16:02 EUVD

CVE Published

Oct 18, 2026 - 15:18 cve.org

UNKNOWN (no severity yet)

Threat Intelligence Overview

EPSS Score

0.2%

Top 89% exploitable

Data Quality

3 sources

Confidence: Low

EUVD

CVE.org

EPSS MSRC

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity Not scored yet

CISA KEV No

Public POC No

EPSS 0.2%

Patch available Yes

Active threat No

Deciding rule

No CVSS yet + weak signal (CWE or non-zero EPSS)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.